The number of factors that play into spectacle lens quality can be overwhelming for opticians and patients alike. The number of lens technologies and materials has grown in recent years. Undoubtedly, many of your patients ask for thin lenses. Thinner lenses are often considered by patients to be more comfortable and appealing. Many dispensing opticians will immediately recommend a high index lens material to fulfill the patient’s request for thin lenses. However, refractive index should not be the first consideration in this scenario. The most important place to always start the lens recommendation is with the patient’s prescription.
Patients with stronger prescriptions will require a high index lens material to achieve their desired lens thinness. However, patients with low to moderate prescriptions will not see any significant difference in lens thinness between lenses with lower and higher refractive indices.
It’s important to note that the majority of your patients’ prescriptions fall into the low to moderate power range. In a monograph published by Younger Optics, Ed De Gennaro reports that 85% of patients’ prescriptions fall within +3D to -3D and only 15% fall within +4D to +12D and -4D to -12D. That means that 8 out of 10 patients will not experience any additional lens thinness with high index lenses when compared to Trivex lenses. Trivex material offers similar thinness as polycarbonate and high index materials while bestowing other benefits many of your patients may value.
No Need to Sacrifice Clarity for Comfort
The Younger Optics study shows that Trivex lenses offer advantages that would better suit many of your patients. Trivex material features a refractive index of 1.53. It does not offer the same thinness of higher-index materials, but it does offer similar thinness. The thickness of Trivex lenses is similar to 92% of total prescriptions when compared to 1.67 high index lenses and 98.8% of total prescriptions when compared to polycarbonate lenses.
In addition to comparable thinness, Trivex material offers unmatched lightness. Trivex material has a specific gravity of of 1.11 g/cm3 -- polycarbonate and other materials have 1.21 or higher. Because of this, Trivex lenses are lighter than all high-index lenses. In fact, 89.9% of Trivex lenses (between +6D and -3D) are 10-16% lighter than 1.67 high-index lenses. Trivex lenses are also lighter than 99.8% of polycarbonate lenses of the same mass.
Trivex material also boasts a higher Abbe value than either polycarbonate or high-index, providing greater optical clarity at any prescription power.
This is not to say Trivex material should become your default recommendation for all of your patients’ lenses. When recommending a lens material to your patients, start with their prescription and then weigh every aspect of the material. Consider the options at hand and the needs of your patients, and remember that for many prescriptions Trivex lenses can be the “thinner lenses” you patients desire while providing even more benefits.